This invention relates to a vertical wafer carrying apparatus and, more particularly to an apparatus for carrying semiconductor wafer in vertical direction in a process for manufacturing semiconductor devices.
In order to improve productivity of semiconductor elements, the diameter of semiconductor wafers has been increased to reach and now is exceeding about 20 cm to about 25 cm. Therefore, the conventional batch type manufacturing process is being rapidly replaced with the single piece flow type employing a conveyor belt and an air bearing.
FIG. 1 illustrates in a perspective view an ordinary air bearing conveyor line for photo-engraving, in which semiconductor wafers 2 successively supplied from a wafer supply cassette 1 are conveyed by air bearings 3 in the direction of the arrows, whereby they are processed at various process stages. In FIG. 1, the photo-engraving is achieved by conveying the semiconductor wafers 2 through a photo-resist coating chamber 4, a prebaking zone 5, a pattern printing machine 6, developing chamber 7, a post baking zone 8, a resist inspector 9, a photo-etching chamber 10, a photo-resist removal chamber 11, a dewatering baking zone 12 and a pattern inspector 13 to a wafer containing cassette 14.
The semiconductor wafer carrying method as above described is satisfactory when the wafers are conveyed in one direction and the same treatments are applied to each wafer. However, it has recently become increasingly necessary that various wafers having different patterns since the demands of customers are mixed and conveyed by a single common conveyer line in making Application Specific ICS (ASICS). For a semiconductor device manufacturing line, changing the arrangement of the line according to the demand of the customer must be avoided because it causes a loss and the line must be automated and dust-free.
For example, in the manufacturing line illustrated in FIG. 1, when a wafer which does not need certain of the illustrated processing chambers, the line management is extremely difficult. Also, when the sampling check for the wafer quality, temporary waiting or wafer storing is necessary, the entire line must be stopped. Further, it is desirable to make such temporary halt or branching of the line possible within a limited space as small as possible.